Prior art panoramic dental X-ray apparatus are well known in the art. Some provide a continuous image of the dental arch area and commonly employ an X-ray source and X-ray film supported on a rotatable carrying arm which orbits a patient situated in the beam path. The dental arch however is not usually circular or elliptical, but represents a complex curve. Mechanisms have been devised which permit the X-ray source and X-ray film to travel about the patient along a curve which closely parallels the complex shape of an ideal dental arch, thus insuring substantially proper focus to each tooth being radiographed.
In addition to insuring proper depth of focus for each tooth, it is essential that the speed of X-ray film travel be adjusted in accordance with the more arcuate shape of the incisors-cuspid area, or anterior region, as compared to the molar-biscuspid area, or posterior region, if proper spacing and distances occupied by each tooth is to be portrayed on the continuous radiograph. Mechanisms for controlling film travel speed; orbiting the X-ray source and X-ray film about the patient; and shifting the chair in accordance with a predetermined pattern; must be painstakingly integrated if meaningful continuous radiographs are to be provided. Such radiographs provide the dentist with a panoramic view of the teeth and associated structures and are useful diagnostic aids in many phases of dental practice.
Various other prior art apparatus provide a discontinuous, or split image panoramic radiograph which possesses certain advantages. Here, the dentist is provided with additional interpretive information since two distinctly different views of the centrals area are provided. For example, consider the split image radiograph as two separate films. A pathology located on the left half is noted with respect to its relationship to the centrals, or incisors. The same pathology is located on the right half. If the image of the pathology, such as an impacted canine, appears to move away from the patient's midline, the pathology is palatally located. Conversely, if the image of the pathology moves toward the midline, it is labially located. Additionally, overlying spinal shadows which would be cast over the central-biscuspid region are eliminated since X-rays are not generated when the spine is aligned with the X-ray source and film.
The present invention discloses a panoramic dental X-ray machine capable of providing either type radiographic image, i.e., continuous or discontinuous.